There are many types of electrical systems that benefit from electrical isolation. Galvanic isolation is a principle of isolating functional sections of electrical systems to prevent current flow, meaning that no direct electrical conduction path is permitted between different functional sections. As one example, certain types of electronic equipment require that high-voltage components (e.g., 1 kV or greater) interface with low-voltage components (e.g., 10V or lower). Examples of such equipment include medical devices and industrial machines that utilize high-voltage in some parts of the system, but have low-voltage control electronics elsewhere within the system. The interface of the high-voltage and low-voltage sides of the system relies upon the transfer of data via some mechanism other than electrical current.
Other types of electrical systems such as signal and power transmission lines can be subjected to voltage surges by lightning, electrostatic discharge, radio frequency transmissions, switching pulses (spikes), and perturbations in power supply. These types of systems can also benefit from electrical isolation.
Electrical isolation can be achieved with a number of different types of devices. Some examples of isolation products include galvanic isolators, opto-couplers, inductive, and capacitive isolators. Previous generations of electronic isolators used two chips in a horizontal configuration with wire bonds between the chips. These wire bonds provide a coupling point for large excursions in the difference between the grounds of the systems being isolated. These excursions can be on the order of 25,000 V/usec.
As mentioned above, electrical isolation can be achieved with capacitive, inductive isolators, optical, and/or RF isolators to transmit data across an isolation boundary. Most isolation solutions utilize data sampling at the receiving end. Many sampled data converters require a precision low jitter clock to sample the input signal to achieve good signal linearity. However, at high clock frequencies, the precision clock becomes a source of electromagnetic interference (EMI) and will cause the system with the device on board to fail certain EMI compliance standards.
While it is desirable to have a quality system clock that has small jitter with the clock centered at the intended frequency, this may impart EMI to other devices in close proximity. To reduce the EMI, system designers often face difficult and complex design considerations and implementations, (e.g., short clock PCB traces, putting the device to be clocked as close as possible to the clock distribution source, and transmission lines matching). While these are based on good design practice, actual EMI is hard to predict and can only be known when actual measurement is performed. Designers risk failing the system EMI compliance test in the end even if the system is designed to accommodate certain amounts of EMI.